Measuring and testing – Probe or probe mounting
Patent
1996-10-17
1998-04-14
Chilcot, Richard
Measuring and testing
Probe or probe mounting
7386491, 204424, G01D 2100, G01N 2726
Patent
active
057394415
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on an arrangement of a sensor wherein the sensor element, in the form of a tube closed at one end, rests with a metallic sealing ring on a seal seat formed on the housing element of an electrochemical measuring sensor in a metallic housing. The sensor elements of the electrochemical measuring sensors are configured, for example, in the so-called finger construction. The sensor element is a solid electrolyte body which is configured as a closed tube and fixed in a gas-tight manner in a metallic housing with a metallic sealing ring. In potential-free finger sensors, the metallic sealing ring must not contact the outer conductor track. For this purpose, the conductor track is coated with an electrically insulating layer upon which pressure is exerted by the sealing ring. A pressing of the edges of the sealing ring into the insulating layer would destroy the insulating layer and the potential-free feature would thus be eliminated. It is the object of the present invention to prevent this.
SUMMARY AND ADVANTAGES OF THE INVENTION
The problems according To the known arrangements are overcome according to the present invention by an arrangement of a sensor element of an electrochemical measuring sensor in a metallic housing, wherein the sensor element, in the form of a tube closed at one end, rests with a metallic sealing ring on a seal seat implemented on the housing, and the seal seat is designed as a raised circular ring surface having a radius (r).
The present invention as described above has the advantage that the sealing ring support line is disposed in the center of the seal seat cone on the sensor element and that a pronounced stress over the surface is present in the joining region between sealing ring and sensor element. This ensures increased production reliability, and the measuring sensor is improved with respect to its gas tightness and resistance to gasoline. The pronounced stress over the surface (wide contact pattern of the sealing ring) prevents possible crack formations in the insulating layer. This also prevents a diffusion of heavy metal ions into the insulating layer, thus maintaining the insulation resistance of the insulating layer even during thermally stressed continuous operation.
It is particularly advantageous to implement the radius for the support of the sealing ring with r=0.5-1.5 mm preferably r=1 mm. This creates a good seal seat which also does not entail any deformation of the sealing ring. Adjoining the radius, a free surface is configured for the sealing ring so that the sealing ring can orient itself tangentially relative to the line-shaped circular support formed by the radius. It is advantageous for the free surface to be cone-shaped.
BRIEF DESCRIPTION OF THE DRAWINGS
Two embodiments of the invention are illustrated in the drawing and explained In greater detail in the description below. FIG. 1 shows a section through a detail of an electrochemical measuring sensor, FIG. 2 shows an enlarged detail X with a first embodiment of a seal seat according to the invention, and FIG. 3 shows the detail X with a second embodiment of a seal seat according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The electrochemical measuring sensor according to FIG. 1, shown in a detail, has a metallic housing 10 with a thread 11 as a fastening means or arrangements for the installation of the sensor in an exhaust gas pipe, not shown, and a sensor element 13. The housing 10 has a longitudinal bore 15 with a seal seat 16. The sensor element 13 with a metallic sealing ring 18 is seated on the seal seat 16.
The sensor element 13 is a tube-shaped solid electrolyte body 20 whose end section 21 is closed on the side of the gas to be measured. On the end section 22 on the side of the connection, the solid electrolyte body 20 is configured as a bulge-shaped head 23 with a ring-shaped front or end face 24.
On the outer side that is exposed to the gas to be measured, a measuring electrode, not shown in detail, is arranged on
REFERENCES:
patent: 4240890 (1980-12-01), Watanabe et al.
patent: 4349203 (1982-09-01), Schulke
patent: 4383906 (1983-05-01), Sano et al.
patent: 4572009 (1986-02-01), Brauer et al.
patent: 5435901 (1995-07-01), Friese et al.
Fries Romuald
Friese Karl-Hermann
Weyl Helmut
Amrozowicz Paul D.
Chilcot Richard
Robert & Bosch GmbH
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